\begin{table}[htbp]\centering
\caption{Diff-in-Diff Results Controlling for Emissions Inspections Programs \label{tab:RegDiDEmissions}}
\begin{tabular}{l*{4}{c}}
\hline \hline \multicolumn{5}{c}{Dep. Var.: Log Number of Vehicle Registrations} \\ &      (1)&      (2)&      (3)&      (4)\\
Removal of      & 0.053***& 0.054***&  0.035**&   0.024*\\
Safety Inspections&  (0.015)&  (0.015)&  (0.014)&  (0.013)\\
\makecell[l]{Data Source \nextline Controls}&     None&Documented&\makecell{Large \nextline Undocumented}&\makecell{Small \nextline Undocumented}\\
State Fixed Effects&        Y&        Y&        Y&        Y\\
Year Fixed Effects&        Y&        Y&        Y&        Y\\
\makecell[l]{State-Specific Linear \\ Time Trends}&        Y&        Y&        Y&        Y\\
\makecell[l]{State-Specific Quadratic \\ Time Trends}&        Y&        Y&        Y&        Y\\
Common Controls &        Y&        Y&        Y&        Y\\
\makecell[l]{Emission Inspections \\ Controls}&        Y&        Y&        Y&        Y\\
Robust F-Stat   &   13.163&   12.989&    6.251&    3.295\\
Number of Obs.  & 2424.000& 2424.000& 2424.000& 2424.000\\
R\textsuperscript{2}&    0.998&    0.998&    0.998&    0.999\\
\hline \hline \end{tabular} \vspace{0.2cm} \begin{tablenotes} \begin{spacing}{0} \begin{footnotesize} \item \textbf{Notes:} This table presents difference-in-differences estimates of the impact of the removal of safety inspections on the log of vehicle registrations.  The unit of observation is state-year. The four specifications pertaining to different levels of  (DSCs) and control specifications are documented in Table \cref{ssec:Spec}. Standard errors, reported in parentheses, are clustered by state. * p\textless 0.1, ** p\textless 0.05, *** p\textless 0.01 \end{footnotesize} \end{spacing} \end{tablenotes} \end{table}
